Anodically stable and highly conducting borane solid state battery electrolytes

Abstract

An inorganic solid state electrolyte includes a metal cation selected from Li + , Na + , Mg 2+ , Ca 2+ , Zn 2+ , or Al 3+ , and a single phase crystalline solution with a first borate cluster anion and at least one second borate cluster anion different than the first borate cluster anion. The first borate cluster anion and the at least one second borate cluster anion have the same number of vertices, but a different number of hydrogens exchanged with a halogen atom selected from F, Cl, Br, I, or a combination thereof. The inorganic solid state electrolyte also has an elastic modulus of less than 15 GPa and supports a coulombic efficiency of metal or alloy anode charging/discharging greater than 99%.

What is claimed is: 
     
         1 . An inorganic solid state electrolyte comprising:
 a metal cation selected from the group consisting of Li + , Na + , Mg 2+ , Ca 2+ , Zn 2+ , and Al 3+ ;   a single phase crystalline solution comprising a first borate cluster anion and at least one second borate cluster anion different than the first borate cluster anion, the first borate cluster anion and the at least one second borate cluster anion having the same number of vertices and a different number of hydrogens exchanged with a halogen atom selected from the group consisting of F, Cl, Br, I, or combinations thereof, or a different number or type of substituents present on each for the first borate cluster anion and the at least one second borate cluster anion; and   an elastic modulus of less than 15 GPa.   
     
     
         2 . The inorganic solid state electrolyte according to  claim 1 , wherein the first borate cluster anion and the at least one second borate cluster ion are selected from the group consisting of [B y H (y-z-i) R z X i ] 2− , [CB (y-1) H (y-z-i) R z X i ] − , [C 2 B (y-2) H (y-t-j-1) R t X j ], [C 2 B (y-3) H (y-t-j) R t X j ] − , or [C 2 B (y-3) H (y-t-j-1) R t X j ] 2− , where y is an integer within a range of 6 to 12; (z+i) is an integer within a range of 0 to y, (t+j) is an integer within a range of 0 to (y-1), X is F, Cl − , Br − , I − , or a combination thereof, and R is a linear, branched-chain, or cyclic C1-C18 alkyl or partially or totally fluorinated alkyl group. 
     
     
         3 . The inorganic solid state electrolyte according to  claim 2 , wherein the first borate cluster anion is a halogenated closo-borate anion and the at least one second borate cluster anion is a halogenated closo-borate anion. 
     
     
         4 . The inorganic solid state electrolyte according to  claim 2 , wherein the first borate cluster anion is a non-halogenated closo-borate anion and the at least one second borate cluster anion is a halogenated closo-borate anion. 
     
     
         5 . The inorganic solid state electrolyte according to  claim 4 , wherein the first borate cluster anion has a first crystalline phase, the at least one second borate cluster anion has a second crystalline phase different than the first crystalline phase, and the single phase crystalline solution has the first crystalline phase. 
     
     
         6 . The inorganic solid state electrolyte according to  claim 5 , wherein the first borate cluster anion is a CB 11 H 12   −  and the second borate cluster anion is CB 11 H 11 X − , where X −  is F − , Cl − , Br − , or I − . 
     
     
         7 . The inorganic solid state electrolyte according to  claim 6 , wherein a concentration, in mole percent, of the second borate cluster anion in the single phase crystalline solution is between about 1 mol % and about 90 mol %. 
     
     
         8 . The inorganic solid state electrolyte according to  claim 6 , wherein the metal cation is Li + , Na + , or a combination thereof. 
     
     
         9 . The inorganic solid state electrolyte according to  claim 6 , wherein a cell volume of the single phase crystalline solution increases with increasing content of the second borate cluster anion. 
     
     
         10 . The inorganic solid state electrolyte according to  claim 6 , wherein the elastic modulus is between about 4 GPa and about 8 GPa. 
     
     
         11 . The inorganic solid state electrolyte according to  claim 1  further comprising one or more additional conductivity enhancing anions, wherein a mole fraction of the one or more additional conductivity enhancing anions to the total anions in the single phase crystalline solution is between about 0.01 to about 0.9, and the one or more additional conductivity enhancing anions is selected from F − , Cl − , Br − , I − , R x BF 4-x   − , R y PF 6-y   − , SbF 6   − , ClO 4   − , SO 4   2 , N(SO 2 F) 2   − , N(SO 2 (CF 2 ) n CF 3 ) 2   − , [NSO 2 (CF 2 ) n+1 SO 2 ] − , or CF 3 (CF 2 ) n SO 3   − , where: n is 0 to 5; x is 0 to 4; y is 0 to 6; and R is a linear, branched, or cyclic alkyl group that can be unsubstituted, partially fluorinated, or fully fluorinated. 
     
     
         12 . An inorganic solid state electrolyte comprising:
 a metal cation selected from the group consisting of Li + , Na + , Mg 2+ , Ca 2+ , Zn 2+ , and Al 3+ ; and   a single phase crystalline solution comprising a non-halogenated closo-borate anion and a halogenated closo-borate cluster anion, the non-halogenated closo-borate anion and the halogenated closo-borate cluster anion having the same number of vertices;   an elastic modulus of between about 1 GPa and about 10 GPa; and   a coulombic efficiency of metal or silicon anode discharge/charge greater than 99%,   wherein the non-halogenated closo-borate anion has a first crystalline phase, the halogenated closo-borate anion has a second crystalline phase different than the first crystalline phase, and the single phase crystalline solution has the first crystalline phase.   
     
     
         13 . The inorganic solid state electrolyte according to  claim 12 , wherein the non-halogenated closo-borate anion is selected from the group consisting of [B y H (y-z) R z ] 2− , [CB (y-1) H (y-z) R z ] − , [C 2 B (y-2) H (y-t-1) R t ] − , [C 2 B (y-3) H (y-t) R t ] − , or [C 2 B (y-3) H (y-t-1) R t ] 2− , and where y is an integer within a range of 6 to 12, z is an integer within a range of 0 to y, t is an integer within a range of 0 to (y-1), and R is a linear, branched-chain, or cyclic C1-C18 alkyl or partially or totally fluorinated alkyl group. 
     
     
         14 . The inorganic solid state electrolyte according to  claim 13 , wherein the halogenated closo-borate anion is selected from the group consisting of [B y H (y-z-i) R 2 X i ] 2− , [CB (y-1) H (y-z-i) R z X i ] − , [C 2 B (y-2) H (y-t-j-1) R t X j ] − , [C 2 B (y-3) H (y-t-j) R t X j ] − , or [C 2 B (y-3) H (y-t-j-1) R t X j ] 2− , where y is an integer within a range of 6 to 12; (z+i) is an integer within a range of 0 to y, (t+j) is an integer within a range of 0 to (y-1), X is F, Cl, Br, I, or a combination thereof, and R is a linear, branched-chain, or cyclic C1-C18 alkyl or partially or totally fluorinated alkyl group. 
     
     
         15 . The inorganic solid state electrolyte according to  claim 14 , wherein the non-halogenated closo-borate anion is CB 11 H 12   −  and the halogenated closo-borate anion is CB 11 H 11 X − . 
     
     
         16 . The inorganic solid state electrolyte according to  claim 15 , wherein a concentration, in mole percent, of the halogenated closo-borate anion in the single phase crystalline solution is between about 1 mol % and about 90 mol %. 
     
     
         17 . The inorganic solid state electrolyte according to  claim 15 , wherein the metal cation is Li + , Na + , or a combination thereof. 
     
     
         18 . The inorganic solid state electrolyte according to  claim 15 , wherein a cell volume of the single phase crystalline solution increases with increasing content of the halogenated closo-borate cluster anion. 
     
     
         19 . An electrochemical cell comprising:
 an anode selected from the group consisting of an intercalation anode, a metal anode, an alloy anode, and an organic anode;   a cathode selected from the group consisting of an insertion cathode, a conversion cathode, and an organic cathode; and   an inorganic solid state electrolyte comprising:
 metal cation selected from the group consisting of Li + , Na + , Mg 2+ , Ca 2+ , Zn 2+ , and Al 3+ ; 
 a single phase crystalline solution comprising a first borate cluster anion and at least one second borate cluster anion different than the first borate cluster anion, the first borate cluster anion and the at least one second borate cluster anion having the same number of vertices and a different number of hydrogens exchanged with a halogen atom selected from the group consisting of F, Cl, Br, I, or combinations thereof, or a different number or type of substituents present on each for the first borate cluster anion and the at least one second borate cluster anion; and 
 an elastic modulus of less than 15 GPa. 
   
     
     
         20 . The inorganic solid state electrolyte according to  claim 19 , wherein a cell volume of the single phase crystalline solution increases with increasing content of the at least one second borate cluster anion.